Raku pottery or Raku ware originated in Japan in the 16th century. The master potter, Chõjirõ, after firing, rapidly cooled his pots. The pots developed almost unseen hairline cracks called crazing. These pots became very popular in the use of the Japanese tea. In Japan during the period, it was consider a great honor to be served with the family’s everyday ware. As the Raku ware was used in the tea ceremony, the crazing would darken from the tea, thus showing its use. This made Raku ware very desirerable. Because of his masterful work, Chõjirõ was given a gold seal bearing the mark Raku. The family adopted the name and continued the firing process that bared their name.
Jumping ahead, many years, Bernard Leach, a famous English potter, while studying in Japan was introduced to Raku ware. Bernard Leach wrote about it briefly in his book. An American potter, Paul Soldner, read about the pots, that were rapidly cooled and the crazing that developed. Paul experimented with removing the pot from the kiln to achieve this effect. To help bring out the crazing, Mr. Soldner combined the Raku process with primitive pit-firing techniques. The combination of Raku and pit-firing introduce smoke to the pots and carbon stained the crazing lines. He would heat the pots up until the glazes started to melt, remove the pots from the kiln and place them in combustibles then cover them. As the covered combustibles burned, it would reduce the oxygen until it starved the fire, thus giving the name to the covered area as a post-fire reduction chamber.
As potters experimented with different glazes, it was found that different chemical in the glaze would achieve looks and effects, including luster and color shifts. The most effected chemical was copper giving multi-colored effects and shines.